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Treasure Valley Onions

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Innovations in onion production have cut water and fertilizer use by half and produced crops of the very largest onions.

Jumbo. Colossal. Super colossal. The superlatives used to rate Treasure Valley onions suggest they could take over the world. And in a way, they have. Many of the onions sold in U.S. grocery stores during fall and winter come from this valley at the border of Oregon and Idaho.

After 20 years of research, scientists at OSU’s Malheur Agricultural Experiment Station have helped Treasure Valley onion producers triple their acreage in onions and reduce water use, pesticides, fertilizer, and runoff. And, in the process, the onions got bigger.

But the story wasn’t always this sweet.

Back in the mid-1980s, years of tractor-operated cultivation had compacted onion fields in Treasure Valley. Traditional furrow irrigation was sending water, fertilizer, and pesticides across the surface of fields, and beyond. Nitrate and residues of the herbicide DCPA seeped through the soil into groundwater.

“We could see regulations were coming down the pipeline,” said Clint Shock, superintendent of the OSU research station, appropriately located on Onion Avenue in Ontario.


Shock experimented with drip irrigation to replace the old furrow system. He was able to apply moisture and fertilizer slowly right to the root zone, keeping topsoil in place and protecting water quality. And, with no water splashing onto onion leaves, drip irrigation reduced the chances of disease.

Shock and colleagues continued their experiments. They developed systems that released water only when sensors indicated that soil moisture had dropped below a particular level. At the same time, breeding programs by private seed companies developed improved onion varieties for Treasure Valley, and growers adopted herbicides that would break down quickly, replacing stronger, long-lived chemicals.

With water and fertilizer dripped directly to the roots in measured amounts—and only when needed—onions grew large and well-centered, perfect for making onion rings. And the results are measurable beyond the onion fields.

“Twenty years of groundwater sampling indicates that residues of the herbicide DCPA are decreasing in the Valley,” said Shock, “and nitrate residues are also starting to decrease, despite the three-fold increase in onion production.”